My grandma is really mad at me?

Ok so I played this prank on my grandma who is about 60 and a really fun grandma and thinking back on it it was really stupid and I should not have done it. So I went on her iPad and put 3 keyboard shortcuts on it. I changed "the" to pickle, and a couple other words. Well, apparently she needs to type and it's important for sending emails to people. So today I texted her about he prank with a few lols cuz I thought it was a harmless joke. So I get this text back: that's not funny. This is my service tool. I was trying to write letters today. I know you'll learn as you mature, but sometimes a joke goes too far. I don't know how to fix this, and I need to. So I sent her instructions on how to fix it and I said I was sorry, and she has not texted me back since. I really am sorry, and I don't know why I did it, but please tell me what to do! Every time I play a prank on anyone they just get really mad at me and I'm sensitive and can't handle it. How do I get my grandma to forgive me?

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